Most flooring materials are currently prepared from polyvinyl chloride (PVC). PVC usually contains significant amounts of phthalate plasticizers (more than about 30% by weight based on PVC) to produce sufficient flexibility and impact strength for flooring material applications. The flooring materials are typically prepared by thermo-mechanical mixing of PVC, phthalate plasticizer, fillers like calcium carbonate and additives followed by a calendaring process to prepare the desired flooring sheets. Examples of various processes are described in the literature and include the following patents incorporated by reference; U.S. Pat. No. 4,826,912, U.S. Pat. No. 4,804,429, U.S. Pat. Nos. 4,225,374, 3,951,714, U.S. Pat. No. 4,605,584, U.S. Pat. Nos. 5,670,237, 5,700,865, and U.S. Pat. No. 5,945,472. There is an interest in developing alternative materials for use in flooring.
Research has been undertaken in some areas of plastics engineering to use biodegradable materials. For example, U.S. Pat. No. 5,883,199 by McCarthy et al., the contents of which are hereby incorporated by reference in their entirety, discloses plastics including aliphatic polyesters that can be blended with PLA (polylactic acid or polylactide) to plasticize the PLA so it can be recycled and used again in packaging. Purportedly, the blends can be used to make biodegradable plastic film, sheets, and other products by conventional processing methods such as blown film, extrusion, and injection molding methods. The resulting blends can be used to manufacture bags, food packaging, laminated papers, food trays, fishing line, net, rope, diapers, disposable medical supplies, sanitary napkins, shampoo, drug, cosmetic, and beverage bottles, cutlery, brushes, combs, molded and extruded foamed articles such as packing material and cups, and cushions for flexible packing. These blends purportedly provide not only the excellent processibility of polyethylene, but also posses properties such as those of polyethylene terephthalate. In addition, these blends can purportedly be processed into films that are heat-sealable, unlike polyethylene terephthalate.
U.S. Pat. Nos. 5,756,651 and 5,908,918 by Chen et. al., the contents of which are hereby incorporated by reference in their entirety, disclose blending polycaprolactone and polyethylene glycol with PLA for packaging film applications. Acetyl tri-n-butyl citrate, sold under the trademark “CITROFLEX A-4” was chosen as a plasticizer for the study based on its degradability, non-toxicity, and compatibility with PLA. Epoxidized soy oil was used as a co-plasticizer in some occasions. With the blown films, about 3% of talc and 1% of calcium stearate were added for anti-blocking purposes.
U.S. Pat. Nos. 5,998,552 and 6,291,597 to Gruber et. al., the contents of which are hereby incorporated by reference in their entirety, teaches preparing a polymer composition by providing PLA polymer molecules which have been modified, relative to linear non-substituted PLA, to provide increased molecular interaction among PLA backbone chains in the composition. The prior art to date appears to have focused on using epoxidized soybean oil, linseed oil and citrate plasticizers with these polymer compositions, and has not applied the technology to the flooring arts.
In light of the growing environmental awareness, increasing societal concern and new environmental rules and regulations, it would be advantageous to have ecologically friendly green materials for flooring applications that provide the flooring with desirable physical and mechanical properties. The present invention provides such materials and flooring.